Adhesives comprising phenol-formaldehyde resins, certain polyvinyl acetal resins and ricinoleate esters



Patented May 5, 1953 UNITE!) Alllll] Slt/'ES COMPRISING PHENOL-FORM- ALDEEEYDE RESINS, CERTAIN POLYVINYL iil'llil.. RESNS AND' R I CIN G LE AT E" No Drawing.

Application July 14, 1956,

Serio-l No. 173,952

i Claims. l

This invention, relates to the art of adhesives and adhesive Films. More sp ally it relates to adhesive com o ons basso on phenol for.- aldehyde condens son products and one or more of. polyvinyl proponal, polyvinyl butyral, polyvinyl pental and polyvinyl heaal.

The polyvinyl aoetals named interact with the phenol formaldehyde condensation products to provide uniform compos?. ions which are substantially more resistant to solvents and have better strength properties either resin alone. The compositions may re lily be applied from solution or' as partially cured normally stable but heat-reactive and. fully cured on the surfaces that they are to bond at the application temperatures and pressures which provide temporary heat softening and good flow or the adhe sive into the suriaee i terstices followed by rapid heat cure and accor 'ly a satisfactory perma nent bond.

However, the above-mentioned have `two important disadvantages:

1. The ultimate shear strength is not as high as is desirable for many industrial applications; and,

2. The compositions are slightly brittle and accordingly sometimes diiioult to handle in solid form.

This invention, therefore, the primary oojeot of providing adhe ive compositions of high ultimate shear strength. A more speciflo object is to provide an adhesive coiriposition compri ng at least one phenol formaldehyde condensation product and at least one of the polyvinyl pro pionals, the polyvinyl hutyrals, the polyvinyl pentals and the polyvio hesals increased ultima-te strength, vrhile at the time preserving and util f all advantageous properties or similar compositions of the priorlart. A further object is. the prot sion of strong adhesive compositions that are enough to permit ready handling. A still further object-is the provision oi' strong, easily handled adhesive compositions that are economical, easy to pren pare and require no expensive equipment either in theirI manufacture or their use. These ob jects as Well as oher important oit-jects Will become* readily yeuoparent those skilled the art from the following description or' the invention.v

The invention is based upon the surprising discovery that the ultimate strength of compositions comprising phenol formaldehyde and one or more of the polyvinyl propionals, the polyvinyl butyrals, the polyvinjl pentals and the. polyvinyl hemels, is improved greatly and the flexibility and ease of handling enhanced if these compositions oontainatotal ol from. at least one compositions quarter of one per cent 'out not more than seven and one half cent by weight of one or more rieinoleate esters, basedV on the combined Weight of the phenol formaldehyde condensation product andthe polyvinyl acetal in the oomposition.

Best overall results andk the highest ultimate shear` strength are obtained if from one to five per 'centrloinoleate 'ester is presentin the composition. If substantially less' than one quarter of a per cent ricinoleate ester is used,` no significant increase in strength or flexibility is observed. lli substantially less than one per cent rilcinoleate ester is used, no signicant improvement in liexibillty and handling is observed. If substantially more than live per cent ricinoleate ester is used the composition is too weak in shear strength for some uses.4 .lf substantially more than seven and one half per cent rioinoleate ester used the composition is too Weak for many important industrial uses.

In those aspects of the invention where it isl desired toV apply a composition comprising phenol iormaldehyde condensation product and one or" the above-named polyvinyl acetals and to cure the composition aftery application, the preferred phenol formaldehyde Condensation product Will be an alkali catalyzed alcohol soluble phenol formaldehyde resin. ln'preferred compositions of this type the ratio of formaldehyde to phenol Will be at least one to one and not more than three to one. Best results will be obtained with ratios of formaldehyde to phenol` of from 1.1 to one to two to one. Where eure after application `is not desired, other phenol formaldehyde resin may be used.. The type oi' polyvinyl acetal is important. Polyvinyl formal polyvinyl acetal show no significant improvements when compounded in accordance with this invention. No significant improvements are notedin compositions using the highest acetals. Best improvement is noted in compositions comprisingl polyvinyl propionals, the polyvinyl butyrals, the polyvinyl pentals and the polyvinyl hexals. Incidentally, the term polyvinyl acetal is used in this speoiio generic meaning to include the group rather than polyvinyl acetal itself,` 'which is unsuitable for purposes of this invention. Whenever mention is niadeherein of any type of aceto-1 as suitable, its isomers are similarly suitable.

Any ricinoleate ester maybe used.. Castor oil is'highly satisfactory. Among other ricinoleate esters that are valuable inthe execution of this invention are: methyl'ricinoleate, ethyliricinoleate, butyl ricinoleate, .methyl acetyl ricinoleate, ethylV acetyl ricinoleate, butyl acetyl rioinoleate,k glyceryl tri-aceto .ricinoleata commeroial castor,n

oil, puried castor oil and the other commercial ricinoleate esters. The more complex esters may also be used e. g. monomethyl ethylene glycol ricinoleate and acetylated monomethyl ethylene glycol ricinoleate.

The preferred compositions of the invention are based on ratios of from forty to seventy-five parts of one or more of the above-mentioned polyvinyl acetals compounded with from sixty to twenty-live parts phenol formaldehyde condensation product. The satisfactory ratios of ricinoleate ester added to one hundred parts of any of the above-mentioned compositions were described earlier in this specification.

To illustrate representative embodiments of the invention by way of example only but not to limit the scope of the invention in any way illustrative embodiments are furnished below:

Example Parts by weight Polyvinyl butyral (7% hydroxyl) (2.6 times greater when calculated as vinyl alcohol) intrinsic viscosity 0.81-'1.16 lin cyclohexanone at C. (specific gravity 1.03) Alcohol soluble curing phenol formaldehyde resin, alkali condensed (ratio of phenol to formaldehyde 1.1 to 1.5) 37 Commercial castor oil 1 A miscible solution of the two resins is prepared. The phenol formaldehyde condensation product is dissolved in alcohol and the polyvinyl butyral in a mixture of alcohol and acetone. Solutions comprising approximately forty per cent solids by weight may be used, although all other solutions of suincient iiuidity to permit ready mixing are satisfactory. The castor oil may be mixed in slowly with the two solutions, i. e., using a conventional wall stirrer or any internal mixer.

The adhesive may be applied as the solution made above or alternatively the adhesive may be cast into a conventional film, for instance, of one mil thickness, using conventional nlm casting equipment and drying for from three to ten minutes at approximately one hundred fty degrees Fahrenheit, and the adhesive may be used in the form of the dry heat-reactive but otherwise stable lm. Alternatively the lm may be cast onto a brous or non-fibrous surface e. g. rope paper or a polyvinyl butyral lm and used in that form. The adhesives are normally cured at from two hundred degrees Fahrenheit to four hundred degrees Fahrenheit for several minutes to several hours after application.

To illustrate the invention even better there follows a table showing examples using various proportions of the ingredients listed.

Table Examples Phenol Formaldehyde Condensation Product es Described on Page 4 Glyceryl Tri-Aceto Rieinolcate do Triethyleno Glycol D-Z-Ethyl Hexoate parts by weight.. Metbylene Blue., do.

, ment over the castor oil-free compositions.

In addition to the principal ingredients there may be added to the composition conventional dyes, catalysts, fillers and plasticizers without substantial effect on the invention. Several aldehyde resins, acetals and/or ricinoleates may be used instead of a single one. If an amount of conventional plasticizer such as triethylene glycol di-Z-ethyl hexoate or triethylene glycol di-Z-ethyl butyrate equal to the amount of castor oil is added, the shear strength is not changed substantially over the shear strength using only the original amount of castor oil. For this reason, the addition of plasticizer other than castor oil is often desirable where increased exibility and the advantages of castor oil are both of impoi-tance. Example 6 of the table illustrates such a composition. Other similar compositions may be based on the many other conventional plasticizers for other phenol formaldehyde condensation products and polyvinyl butyrals.

It should be noted that in most compositions of the invention a maximum shear strength is reached using one part ricinoleate ester per one hundred parts of resin regardless of the other ingredients present. A substantial increase in shear strength of the compositions free of castor oil can be noted when one per cent castor oil is used and compositions comprising as much as eight per cent castor oil still show some improve- For instance, using thirty-seven parts of phenol aldehyde condensation product and sixty-three parts of polyvinyl butyral, addition of one-quarter of one per cent of castor oil produces an improvement in shear strength of thirty-five per cent, addition of one per cent produces an improvement of one hundred and ten per cent, while addition of five per cent produces an improvement of only seventy per cent and addition of larger amounts of castor oil steadily lessens the improvement until virtually none may be observed aiter addition of approximately ten per cent.

The invention provides a simple and convenient way of increasing exibility and shear strength of adhesives based on certain polyvinyl acetals and phenol formaldehyde condensation products. The products of the invention are useful for many applications, wherever strength in adhesives is desired, for instance, in the construction industry, in lamination, in the electrical industry and in many other fields.

While the invention has been described in a few of its preferred forms this description is not intended to be by way of limitation but merely by way of illustration and the invention includes many equivalents obvious to those skilled in the art reading this specilication.

The claims are:

1. an adhesive composition comprising a synthetic resin base including from about twentynve to about sixty parts by weight of phenol formaldehyde condensation product and from about forty to about seventy-five parts by Weight of at least one polyvinyl acetal selected from the group consisting of the polyvinyl propionals, the polyvinyl bntyrals, the polyvinyl pentals and the polyvinyl hexals, and from about one-quarter of one per cent to about seven and one-half per cent by weight, based on the total of said condensation product and said polyvinyl acetal, of at least one ricinoleate ester.

2. An adhesive composition comprising a synthetic resin base including from about twentyve to about sixty parts by weight of phenol formaldehyde condensation product and from about forty to about seventy-five parts by weight of at least one polyvinyl acetal selected from the group consisting of the polyvinyl propionals, the polyvinyl butyrals, the polyvinyl pentals and the polyvinyl hexals, and from about one per cent to about ve per cent by Weight, based on the total of said condensation product and said polyvinyl acetal, of at least one ricinoleate ester.

3. An adhesive composition comprising a synthetic resin base including from about twentyfive to about sixty parts by weight of phenol formaldehyde condensation product and from about forty to about seventy-live parts by weight of at least one polyvinyl acetal selected from the group consisting of the polyvinyl propionals, the polyvinyl butyrals, the polyvinyl pentals and the polyvinyl hexals, and from about one-quarter of one per cent to about seven and one-half per cent by weight, based on the total of said condensation product and said polyvinyl acetal, of castor oil.

4. An adhesive composition comprising a synthetic resin base including from about twentyfive to about sixty parts by weight of phenol formaldehyde condensation product and from about forty to about seventy-five parts by weight of polyvinyl butyral and from about one-quarter of one per cent to about Seven and one-half per cent by weight, based on the total of said condensation product and said polyvinyl butyral, of at least one ricinoleate ester.

5. An adhesive composition comprising a synthetic resin base including from about twentyve to about sixty parts by weight of phenol formaldehyde condensation product and from about forty to about seventy-five parts by weight of polyvinyl pental and from about one-quarter of one per cent to about seven and one-half per cent by weight, based on the total of said condensation product and said polyvinyl pental, of at least one ricinoleate ester.

6. An adhesive composition comprising a synthetic resin base including from about twentyfive to about sixty parts by weight of alcohol soluble alkali condensed phenol formaldehyde condensation product, having a formaldehyde to phenol ratio of from about 1.1 to one to about two to one, and from about forty to about seventyve parts by weight of at least one polyvinyl acetal selected from the group consisting of the polyvinyl propionals, the polyvinyl butyrals, the polyvinyl pentals and the polyvinyl hexals and from about one-quarter of one per cent to about seven and one-half per cent by weight, based on the total of said condensation product and said polyvinyl acetal, of at least one ricinoleate ester.

7. An adhesive composition comprising a synthetic resin base including from about twentyve to about sixty parts by weight of alcohol soluble alkali condensed phenol formaldehyde condensation product, having a formaldehyde to phenol ratio of from about 1.1 to one to about two to one, and from about forty to about seventy.. ve parts by weight of polyvinyl butyral and from about one per cent to about ve per cent by weight, based on the total of said condensation product and said polyvinyl butyral, of castor oil.

MILTON A. BERGSTEDT. ROBERT H. LAMASON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,396,098 Haas Mar. 5, 1946 2,433,098 Debacher Dec. 23, 1947 2,442,018 Quarles May 25, 1948 OTHER REFERENCES Baekeland, J. Ind. and Eng. Chem., March 1909, page 155. 

1. AN ADHESIVE COMPOSITION COMPRISING A SYNTHETIC RESIN BASE INCLUDING FROM ABOUT TWENTYFIVE TO ABOUT SIXTY PARTS BY WEIGHT OF PHENOL FORMALDEHYDE CONDENSATION PRODUCT AND FROM ABOUT FORTY TO ABOUT SEVENTY-FIVE PARTS BY WEIGHT OF AT LEAST ONE POLYVINYL ACETAL SELECTED FROM THE GROUP CONSISTING OF THE POLYVINYL PROPIONALS, THE POLYVINYL BUTYRALS, THE POLYVINYL PENTALS AND THE POLYVINYL HEXALS, AND FROM ABOUT ONE-QUARTER OF ONE PER CENT TO ABOUT SEVEN AND ONE-HALF PER CENT BY WEIGHT, BASED ON THE TOTAL OF SAID CONDENSATION PRODUCT AND SAID POLYVINYL ACETAL, OF AT LEAST ONE RICINOLEATE ESTER. 